What can be height of an extrusion or an intrusion which is responsible for crack initiation in case of fatigue (in cm?

What can be height of an extrusion or an intrusion which is responsibl

1.	What can be height of an extrusion or an intrusion which is responsible for crack initiation in case of fatigue (in cm?
A.	2*10<sup>-6</sup>
B.	2*10<sup>-8</sup>
C.	10<sup>-5</sup>
D.	10<sup>-8</sup>
Answer» B. 2*10<sup>-8</sup>